1. Field of the Invention
The present invention relates to an apparatus for feeding a single sheet from the bottom of a stack of sheets, one at a time. Such an apparatus finds practical use in connection with systems where a sheet of paper is to be fed to a station for performing subsequent operations on the sheet, such as placing the sheet in an envelope. Usually, the sheets which can be paper, cardboard, booklets, etc. are stacked in a magazine and the sheets are conveyed by various known apparatus to an envelope where they are inserted by machine. It is highly desirable to perform this conveyance and insertion of the sheet in the envelope as quickly and as safely as possible. The apparatus of this invention may also be used for feeding sheets for printing, wrapping and other type operations where it is highly desirable to rapidly and safely feed a single sheet from a stack of such sheets.
2. Prior Art
In the past apparatus have been devised for feeding sheets one at a time off the top or the bottom of a stack of sheets. As is well known, it is extremely difficult to devise such an apparatus which will unfailingly remove one sheet, and only one, at each movement.
In the top feeding apparatus, one or more vacuum cups are lowered down on the top sheet in the stack to grip the top sheet and lift it off the stack. The vacuum cups are moved upwardly and downwardly until the top sheet is clear of the stack and in a position for processing. The vacuum in the vacuum cup is then cut off to drop the separated sheet into the suitable sheet processing apparatus while the vacuum cups are then moved back to the stack of sheets. The top feeding apparatus has the disadvantage that fresh sheets of paper cannot be loaded on top of the stack while the feeding apparatus is in operation. Accordingly, the feeding mechanism must be stopped when loading is necessary.
The prior art bottom feeding apparatus circumvents the above noted disadvantage but introduces other disadvantages. In such a prior art bottom feeding apparatus a stack of paper sheets, for example, is supported in a hopper or magazine having an open bottom. Means are then provided for removing the sheets from the magazine and conveying the sheets to a receiving and feeding station which then feeds the sheets to another station for performing subsequent operations on the sheets, for example, placing them in envelopes. The disadvantages, generally, of such bottom feeding apparatus (as well as top feeding apparatus) are that they are relatively complicated and expensive. In addition, it is difficult to insure against withdrawal of more than one sheet at a time.
The known prior art is exemplified by the following U.S. Pat. Nos.:
2,524,417 to Bamber; PA1 2,569,219 to Bamber et al.; PA1 2,590,222 to Van Veen; PA1 2,643,120 to Jackson; PA1 3,181,860 to Liebenow et al.; PA1 3,851,871 to Aronson; PA1 3,926,427 to Moksnes et al.; and PA1 4,184,670 to Rosendahl.
Bamber and Bamber et al. remove sheets from a bottomless holder or magazine having two fixed ledges. At least one suction nozzle is provided beneath the pile. The suction nozzle is first brought into contact with the lower most sheet and caused to grip the sheet by suction. The suction nozzle is then moved rearwardly with respect to the direction in which the envelope is to be fed so as to disengage the forward edge of the sheet from one of the ledges. The sheet is then lowered away from the bottom of the stack and then moved forwardly so as to detach the lowermost sheet from the stack and deliver it to a means for carrying away the sheet. Such a motion requires a complicated mechanism to move the suction nozzle backwards, down and then forward.
Van Veen is another example of a complicated apparatus. Van Veen describes two opposed hoppers which hold the sheet to be fed. Two sets of picker fingers are provided for each hopper. The set of picker fingers move into contact with the sheet at the lower of the hoppers. Suction is provided to cause a suction to the set of picker fingers so that they will draw the sheet in the respective hopper against the finger. The fingers are then swung away from the hopper while simultaneously the opposite set of fingers are swung toward its respective hopper. The paper is then stripped from the picker. The mechanism for stripping the paper from the picker requires a stripper plate which moves up and down and requires the paper to flow in a vertical position, as opposed to the normal flow in most unit of horizontal. The stripper plate requires a cam, frame, etc. and is complicated to operate.
Jackson is directed to a sucker arranged beneath a stack of sheets which moves in a vertical position in a complicated arrangement of members. Jackson is able to withdraw one sheet at a time by arranging the sucker so that part of the aperture projects beyond the edge of the pile of blank sheets. Such an arrangement requires the exact placement of the sucker and does not allow for shifting of the apparatus or sheets within the magazine.
Liebenow et al. employes a group of suction cups supported on a traverse bar which is moved in feed and return strokes by a complicated apparatus. The bar is rockable about its longitudinal axis. Each cup is supported in spaced relation from the bar by a flexible conduit which is resiliently yieldable so that the cup can tilt in any direction away from vertical to seat squarely against the engaged face of the blank page. The method by which the bar moves through feed and return strokes is complicated and includes a means to automatically move the bar which holds the suction cup through a continual cycle of horizontal and vertical reciprocation during the feed operation.
Aronson describes a bottom feed magazine for holding sheets but requires that the sheet feed member have imparted thereto a reverse movement of counter rotation which provides a small buckling of sheets held thereby. This buckling frees the lower most sheet from the next adjacent single sheet and insures feeding even at high speeds. Such an arrangement is fairly complicated when compared to applicant's herein described and claimed invention.
Moksnes et al. describes a row of vacuum cups affixed to the upper portion of belt on a shuttle. The vacuum cups are activated with a vacuum to grasp the corner of the lower most sheet of the stack. The shuttles are then reciprocated to the left. The vacuum cups get drawn downwardly around the end of the moving shuttle and then beneath the shuttles to deflect the end of the lower most sheet into a gap.
Rosendahl describes a sheet of paper being sucked out of a stack by rotating roller into feed roller.
Most, if not all of the aforementioned references describe an apparatus which is complicated in nature, expensive to construct and still does not insure the rapid feeding of one sheet at a time from the bottom of a feed magazine.